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(2015) Question 89: For an equipment revamp/replacement, what are the factors you consider when choosing between hot-wall and cold-wall refractory design, including advantages and disadvantages of each?

Shell has experience with both cold-wall and hot-wall refractory designs for reactors and stripper vessels, but regenerator vessels are always cold-wall refractory designs. Depending on the reactor and stripper vessel, refractory type and standpipes, liftpots, and external portions of the riser can be either cold-wall or hot-wall designs.
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(2015) Question 90: We are planning to purchase a new flue gas steam generator. What is your preferred configuration? What are the critical operating parameters you employ to ensure reliable operation? What is your sparing philosophy?

The configuration of the flue gas steam generator will be predominantly governed by FCC design. For a partial-combustion unit, it will be a CO boiler or a CO incinerator cum FGC (flue gas cooler) combination. For complete combustion, it will be a FGC or waste heat boiler alone. By CO boiler, typically we mean a boiler where the steam generating tubes are exposed to direct flame.
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(2015) Question 91: What are your top three causes of unit slowdowns, and what is the loss in onstream factor for each? Please provide the same information for your top three causes of unit shutdowns.

FCC/RFCC units are the one of the major secondary units in almost all of IOCL’s refineries. Irrespective of demand positions, these units are always required to operate at high capacities. All of our refineries had been participating in the benchmarking surveys conducted by Solomon Associates, and the results comparing IOCL FCC units with rest of the world (2014 study) are indicated below.
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(2014) Question 3: What considerations do you make in determining the need for a safety instrumented system (SIS) in an Isomerization unit? What safety integrity level (SIL) do you use for temperature excursions, liquids fed to the regeneration superheater, or other significant safety events? What typical unit design features do you implement to mitigate these safety events?

For chlorided-alumina catalyst systems (Penex™ and Butamer™ units), the top hazard events for which interlock systems are provided are: Reactor temperature excursion Excessive Temperature in Regenerant (Electric) Superheater.
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(2014) Question 5: What are your experiences with alternatives to gauge glasses in alkylation units? Are there any specific services where you prefer glass gauges?

Although gauge glasses can and have been used successfully in HF service, it is essential that proper design and very special operating procedures be followed in order to prevent serious incidents. In the past, gauge glasses were sometimes the only option to provide a reliable secondary indication of liquid levels in the HF Alky units in order to verify the sometimes-unreliable primary level instruments.
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